Silicone composition crosslinkable into elastomer by hydrosilylation, in the presence of carbene-based metal catalysts, and catalysts

ABSTRACT

The invention concerns a silicone composition crosslinkable into elastomer by hydrosilylation, in the presence of carbene-based metal catalysts. The invention aims at providing a composition of that type, stable over long periods at room temperature (one day to several months), without loss of its characteristic of being heat-curable by hydrosilylation and without generating secondary isomerization or colouring reactions. The invention is characterised in that the composition comprises: a polyorganovinylsiloxane (polydimethyl)(methylvinyl) siloxane; a polyorganohydrogenosiloxane; a platinum catalyst formed by a complex of formula C3 and optionally an acetylene crosslinking inhibitor, optionally a siliceous filler. The invention also concerns novel hydrosilylation catalysts of the metal complex type of formula C3 above. The life span of the potted single-constituent compositions of the invention is significantly increased.

[0001] The invention relates to the catalysis of hydrosilylationreactions and especially for the hydrosilylation of ethylenically and/oracetylenically unsaturated compounds (for example olefins or acetylenicderivatives), in particular those involving polyorganosiloxanes (POS)bearing Si—H units and POSs bearing Si-(ethylenic or acetylenicunsaturation) units.

[0002] More specifically, the invention relates to silicone compositionsthat are crosslinkable—preferably into elastomers—by hydrosilylation ofat least one polyorganosiloxane-A-(POS) bearing ethylenic and/oracetylenic unsaturation(s), using at least onepolyorganohydrogenosiloxane -B-, in the presence of a metallic catalyst-C- and optionally comprising at least one inhibitor -D- of thehydrosilylation reaction.

[0003] Conventionally, hydrosilylation reactions that allow silicones tocrosslink are catalyzed via platinum-catalysts (U.S. Pat. No. 2,823,218,U.S. Pat. No. 2,970,150). In practice, to date, the majority ofindustrial hydrosilylation reactions are catalyzed with Karstedtsolution, which consists of complexes of platinum in oxidation state 0.The ideal general formula of the Karstedt complex isPt₂(tetramethyldivinylsiloxane)₃:

[0004] in which Me represents methyl.

[0005] The Karstedt complex is prepared by placing1,3-divinyltetramethyldisiloxane in contact with chloroplatinic acid(H₂PtCl₆), in the presence of NaHCO₃ and an aqueous-alcoholic solvent(isopropanol).

[0006] This common catalyst and its production are described in patentU.S. Pat. No. 3,775,452.

[0007] The very high catalytic activity of this type of catalyst, evenat room temperature, is a major drawback in the context of its use inEVC polyadditions, since the crosslinking of the elastomer starts assoon as all the components are placed in contact.

[0008] Another drawback of this catalyst lies in a possible instabilityof the catalyst during reaction: the precipitation of metallic platinumand the formation of insoluble colloids in the reaction medium have beenobserved: this instability of the catalyst in the reaction medium hasthe effect of reducing the catalytic activity. Furthermore, it resultsin products that are occasionally colored, which are not particularlyappreciated by users.

[0009] Another major drawback of the Karstedt catalyst is theconcomitant formation of side products of the hydrosilylation reaction:products resulting from isomerization reactions of the olefinic doublebond and/or of hydrogenation reactions are isolated along with thehydrosilylation products.

[0010] The unpublished patent application FR 99/15432 of Dec. 7, 1999discloses metallic complexes that are useful as hydrosilylationcatalysts, of formula:

[0011] in which:

[0012] R₃ represents a hydrogen atom; a (C₁-C₈)alkyl group; or

[0013] a (C₃-C₈)cycloalkyl group optionally substituted with (C₁-C₄)alkyl;

[0014] T₁ and T₂ are identical and represent (C₁-C₈)alkyl or(C₃-C₈)cycloalkyl;

[0015] R_(d) and R_(e) are identical and represent (C₁-C₈)alkyl or(C₃-C₈) cycloalkyl;

[0016] (preferably, T₁=T₂=R_(d)=R_(e)=methyl).

[0017] These Pt/carbene metallic complexes are obtained according to atwo-step methodology illustrated by the following example:

[0018] 1. Preparation of the Carbene:

[0019] 2. Preparation of the Platinum Complex of Formula:

[0020] According to this unpublished prior patent application, thecatalysts are used to catalyze the reaction of a compound containing anethylenic double bond or an acetylenic triple bond (unsaturatedcompound) with a compound containing at least one ≡Si—H unit so as toform a C—Si bond. Examples of compounds containing an ethylenic doublebond are ethylene, propylene, 1-butylene, 1-pentene, 2-methyl-1-butene,1-hexene, 1-heptene, 1-octene, 3-ethyl-1-hexene, 1-decene,4,4-dimethyl-1-nonene, vinylcyclohexene, styrene and 2-vinylnaphthalene.

[0021] Examples of compounds containing an acetylenic triple bond are:ethynyl, 2-propynyl, 1-propynyl and 2-penten-4-ynyl.

[0022] Examples of compounds containing at least one ≡Si—H unit arepolymethylhydrogenosiloxane, polydimethylsiloxane containing an —SiH endgroup, methylhydrogenodimethylsiloxane copolymers,methylhydrogenomethyloctylsiloxane copolymers andmethylhydrogenocyclosiloxane polymers.

[0023] Patent U.S. Pat. No. 5,728,839 also discloses metal/carbenecomplexes, prepared in two steps from imidazolium, benzimidazolium,triazolium, tetrazolium or pyrazolium salts (for example iodide). Thesemetallic (rhodium) complexes with heterocyclic carbenes are described aspossibly being useful as catalysts for the hydrogenation orhydroformylation of unsaturated organic compounds, such as olefins. ThatUS patent does not concern the crosslinking of silicones.

[0024] Now, it might be advantageous to have available, in the field ofcrosslinkable silicones—especially into elastomers—catalysts, that areactive at elevated temperature and that show little or no activity atroom temperature. This would make it possible to formulate one-componentsilicones, which are crosslinkable at elevated temperature and stable onstorage for long periods at room temperature (pot life). One-componentsilicone compositions are those comprising in the same mixture all thereactive species (POS Si-vinyl/POS Si—H) and the catalyst.Conventionally, to increase the pot life of one-component siliconecompositions, use is made of crosslinking inhibitors. Thus, with theKarstedt catalyst, the use of an inhibitor is imperative and allows thestability at room temperature of a POS Si-vinyl/POS Si—H composition topass, for example, from 1 minute to 24 hours. However, this is anexpensive solution with limited performance qualities, since the use oflarge amounts of inhibitor is liable to disrupt the behavior of theelastomer during its crosslinking.

[0025] With such a state of the art, one of the essential objectives ofthe invention is to propose a hydrosilylation-crosslinkable siliconecomposition comprising as catalyst one or more heterocycliccarbene-based metallic complexes, this catalyst having low activity atroom temperature, so as to allow the preparation of one-componentcompositions comprising the catalyst and of compounds capable ofreacting at elevated temperature by hydrosilylation of unsaturated units(e.g. POS SiH/POS Si-alkenyl), while at the same time being stable atroom temperature for long periods (e.g. from one day to several months).

[0026] Another essential objective of the invention is to propose ahydrosilylation-crosslinkable silicone composition comprising ascatalyst one or more heterocyclic carbene-based metallic complexes, thiscomposition not being the site, during the crosslinking, ofisomerization side reactions or of colorations liable to disrupt thehydrosilylation.

[0027] Another essential objective of the invention is to propose novelheterocyclic carbene-based metallic complexes that may be used ashydrosilylation catalysts, these catalysts needing to be stable in thereaction medium, so as to limit the formation:

[0028] of undesirable side products resulting from isomerizationreactions of the olefinic double bond and/or hydrogenation reactions,

[0029] and/or of side products that are the cause of colorations thatare just as poorly appreciated.

[0030] Another essential objective of the invention is to propose novelheterocyclic carbene-based metallic complexes that may be used ashydrosilylation catalysts, these catalysts needing to produce selectivecatalytic activity of a high qualitative and quantitative level in thereaction medium.

[0031] Another essential objective of the invention is to propose novelheterocyclic carbene-based metallic complexes that may be used ashydrosilylation catalysts, these catalysts needing to be very active atelevated temperature and to have little or no activity at roomtemperature, so as to be-able to formulate one-component siliconecompositions that are crosslinkable at elevated temperature and stableon storage for long periods at room temperature (pot life), and toachieve this with little or no crosslinking inhibitor.

[0032] Another essential objective of the invention is to propose ahydrosilylation process, in particular for the hydrosilylation ofethylenically and/or acetylenically unsaturated compounds, in thepresence of a catalyst comprising the abovementioned novel-metalliccomplexes.

[0033] These objectives, among others, are achieved by the presentinvention, which relates firstly to a hydrosilylation-crosslinkablesilicone composition of at least one polyorganosiloxane -A- (POS)bearing ethylenic and/or acetylenic unsaturation(s), using at least onepolyorganohydrogenosiloxane -B-, in the presence of a metallic catalyst-C- and optionally comprising at least one inhibitor -D- of thehydrosilylation reaction;

[0034] characterized in that the catalyst -C- comprises at least onecompound selected from the products of formula (I):

[0035] in which

[0036] M represents a metal chosen from the metals of group 8 of thePeriodic Table as published in the Handbook of Chemistry and Physics,65^(th) Edition, 1984-1985;

[0037] L_(γ) represents a carbene of formula (II):

[0038] in which:

[0039] A and B independently represent C or N, it being understood thatwhen A represents N, then T₄ represents nothing, and when B representsN, then T₃ represents nothing;

[0040] T₃ and T₄ independently represent a hydrogen atom; an alkylgroup; a cycloalkyl group optionally substituted with alkyl or alkoxy;an aryl group optionally substituted with alkyl or alkoxy; an alkenylgroup; an alkynyl group; or an arylalkyl group in which the aryl portionis optionally substituted with alkyl or alkoxy; or alternatively

[0041] T₃ and T₄ may form, together with A and B when these eachrepresent a carbon atom, an aryl;

[0042] T₁ and T₂ independently represent an alkyl group; an alkyl groupoptionally substituted with alkyl; a perfluorinated alkyl group or analkyl group optionally substituted with a perfluoroalkyl group; acycloalkyl group optionally substituted with alkyl or alkoxy; an arylgroup optionally substituted with alkyl or alkoxy; an alkenyl group; analkynyl group; or an arylalkyl group in which the aryl portion isoptionally substituted with alkyl or alkoxy; or alternatively

[0043] T₁ and T₂ independently represent a monovalent radical of formula(V) below:

V₁-V₂  (V)

[0044] in which:

[0045] V₁ is a divalent hydrocarbon-based radical, preferably analkylene,

[0046] V₂ is a monovalent radical chosen from the following group ofsubstituents:

[0047] alkoxy, —OR^(o) with R^(o) corresponding to hydrogen, alkyl oraryl

[0048] amine, preferably N(R^(o))₂ with R^(o) corresponding to hydrogen,alkyl or aryl

[0049] T₁ and T₂ independently represent a monovalent radical of formula(W) below:

W₁-ω-W₂  (W)

[0050] in which:

[0051] W₁ is a divalent hydrocarbon-based radical, preferably anoptionally substituted linear or branched C₁-C₁₀ alkylene,

[0052] ω represents:

—R¹C═CR¹—

[0053] with R¹ corresponding to H or alkyl or

—C≡C—

[0054] W₂ is a monovalent radical chosen from the group of the followingsubstituents

[0055] R²=alkyl, H;

[0056] Si-alkyl or Si-alkoxy, preferably —Si(R³)₃ with R³=alkyl;

[0057] alcohol, preferably —C(R⁴)₂OH with R⁴═H or alkyl;

[0058] ketone, preferably:

[0059]  with R⁵=alkyl;

[0060] carboxyl, preferably

[0061]  with R⁶=alkyl;

[0062] amide, preferably

[0063]  with R⁷═H, alkyl;

[0064] acyl, preferably

[0065]  with R⁸=alkyl;

[0066] or alternatively

[0067] the substituents T₁, T₂, T₃ and T₄ may form in pairs, when theyare located on two adjacent ring members in formula (II), a saturated orunsaturated hydrocarbon-based chain;

[0068] L_(α) 0 and L_(β) are ligands that may be identical or different,and

[0069] each represent:

[0070] with, in these formulae (III.1) and (III.2):

Z¹, Z², Z³, Z⁴, Z⁵ , Z⁶

[0071] each independently representing:

[0072]  a. hydrogen,

[0073]  b. a halogen,

[0074]  c. a cyano,

[0075]  d. a saturated or unsaturated electron-withdrawinghydrocarbon-based group, preferably adjacent to the double or triplebond,

[0076]  e. two vicinal Z^(1 to 6) together possibly forming anelectron-withdrawing ring advantageously different than the carbeneL_(γ) of formula (II) and optionally comprising hetero atoms (preferablyO, N or S);

[0077] or the substituents Z¹ and Z² together form, in (III.1), amonovalent alkenyl radical comprising at least one electron-withdrawingresidue preferably adjacent to the triple bond;

[0078] or alternatively Z³ to Z⁶ form in pairs, in (III.2), a monovalentalkenyl radical comprising at least one electron-withdrawing residuepreferably adjacent to the double bond;

[0079] or together form the ligand Lδ of formula (IV):

[0080] in which:

[0081] Y₁ and Y₂ represent, independently of each other, CR_(a)R_(b) orSi_(c)R_(d);

[0082] X represents O, NR_(e) or CR_(f)R_(g);

[0083] R¹⁰, R¹¹, R¹³ and R¹⁴, which may be identical or different, arechosen from a hydrogen atom, an alkyl group and an aryl group optionallysubstituted with alkyl;

[0084] R⁹, R¹², R_(a), R_(b), R_(c) and R_(d) are chosen independentlyfrom a hydrogen atom; an alkyl group; an acyl group; an aryl groupoptionally substituted with alkyl; a cycloalkyl group optionallysubstituted with alkyl; and an arylalkyl group in which the aryl portionis optionally substituted with alkyl;

[0085] R_(c) and R_(d) are independently chosen from alkyl; aryloptionally substituted with alkyl; cycloalkyl optionally substitued withalkyl; and arylalkyl in which the aryl portion is optionally substitutedwith alkyl; or alternatively

[0086] when Y₁ and Y₂ independently represent SiR_(c)R_(d), two groupsR_(c) linked to two different silicon atoms together form a chain offormula:

[0087] in which n is an integer from 1 to 3; X is as defined above; Rand R′, which may be identical or different, take any of the meaningsgiven above for R_(e), it being understood that when n is 2 or 3, onlyone silicon atom of said chain may be substituted with one or twoalkenyl or alkynyl groups; or alternatively when Y₁ and Y₂ independentlyrepresent SiR_(c)R_(d), two groups R_(c) linked to different siliconatoms together form a saturated hydrocarbon-based chain, the two groupsR_(c) together with said silicon atoms and X forming a 6- to 10-memberedring; or alternatively

[0088] when Y₁ and Y₂ independently represent CR_(a)R_(b), two groupsR_(a) linked to different carbon atoms together form a saturatedhydrocarbon-based chain, the two groups R_(a) together with the carbonatoms that bear them and X form a 6- to 10-membered ring; and

[0089] R_(f) and R_(g) represent, independently of each other, ahydrogen atom; an alkyl group; an acyl group; an aryl group optionallysubstituted with alkyl; a cycloalkyl group optionally substituted withalkyl; an arylalkyl group in which the aryl portion is optionallysubstituted with alkyl; a halogen atom; an alkenyl group; an alkynylgroup; or a group SiG₁G₂G₃ in which G₁, G₂ and G₃ are, independently ofeach other, alkyl; alkoxy; aryl optionally substituted with alkyl oralkoxy; or arylalkyl in which the aryl portion is optionally substitutedwith alkyl or alkoxy.

[0090] The presence of the specific metal/heterocyclic carbene complexesin the compositions according to the invention give them great stabilityin ambient atmosphere under normal temperature, humidity and pressureconditions. Such silicone compositions may be stored in one-componentform, in the non-crosslinked state, in ambient atmosphere, for very longperiods (for example from one to several months). This result is all themore advantageous and surprising since, with certain metal/heterocycliccarbene catalysts, it is possible to dispense with using crosslinkinginhibitors or at the very least to use a smaller amount of them, whichis entirely beneficial in economic terms and as regards limiting thenegative repercussions on the crosslinking of the elastomer and itsfinal qualities.

[0091] This stability goes hand in hand with the ability of thecompositions according to the invention to crosslink at elevatedtemperature (for example at and above 100° C.) by hydrosilylation, intoelastomers of high quality, especially of high structural and mechanicalquality. In addition, the reaction kinetics are satisfactory.

[0092] Moreover, no isomerization side reactions and very littleundesirable colorations are observed after crosslinking the compositionsaccording to the invention.

[0093] These one-component silicone compositions, which have a longshelf life at room temperature, are all the more advantageous since theyare not prohibitively expensive. This-advantage is even more pronouncedwhen they do not comprise an inhibitor.

[0094] The definition of the metallic complexes of formula (I)constituting the catalyst C, which is the essential compound of thecomposition according to the invention, is completed hereinbelow.

[0095] The metals of group 8 represented by M in formula (I) are, forexample, palladium, platinum or nickel in oxidation state 0. Inpractice, M represents platinum in oxidation state 0.

[0096] The term “alkyl” denotes a linear or branched, saturatedhydrocarbon-based chain, which is optionally substituted (e.g. with oneor more alkyls), preferably of from 1 to 10 carbon atoms, for examplefrom 1 to 8 carbon atoms and better still from 1 to 7 carbon atoms.

[0097] Examples of alkyl groups are especially methyl, ethyl, isopropyl,n-propyl, tert-butyl, isobutyl, n-butyl, n-pentyl, isoamyl and1,1dimethylpropyl. The alkyl portion of the alkoxy radical is as definedabove.

[0098] The term “cycloalkyl” means a mono- or polycyclic, preferablymono- or bicyclic, saturated hydrocarbon-based radical preferablycontaining from 3 to 10 carbon atoms and better still from 3 to 8 carbonatoms. The expression “polycyclic saturated hydrocarbon-based radical”means a radical containing two or more cyclic nuclei linked together viaσ bonds and/or fused in pairs. Examples of polycyclic cycloalkyl groupsare adamantane and norbornane. Examples of monocyclic cycloalkyl groupsare cyclopropyl, cyclobutyl, cyclpentyl, cyclohexyl, cycloheptyl andcyclooctyl.

[0099] The term “perfluoroalkyl” denotes an alkyl comprising at leastone perfluoroalkyl group, preferably having the formula:

—(CH₂)_(p)—C_(q)F_(2q+1)

[0100] in which p represents 0, 1, 2, 3 or 4; q is an integer from 1 to10; and C_(q)F_(2q+1) is linear or branched. Preferred examples of thisradical are:

—(CH₂)₂—(CF₂)₅—CF₃and —(CF₂)₇—CF₃.

[0101] The term “aryl” denotes a monocyclic or polycyclic, andpreferably monocyclic or bicyclic, aromatic hydrocarbon-based groupcontaining from 6 to 18 carbon atoms. It should be understood that, inthe context of the invention, the term “polycyclic aromatic radical”means a radical containing two or more aromatic nuclei, which are fused(ortho-fused or ortho- and peri-fused) together, i.e. having, in pairs,at least two carbons in common.

[0102] Said aromatic hydrocarbon-based group (“aryl”) is optionallysubstituted, for example, with one or more C₁-C₃ alkyls, one or morehalohydrocarbon-based radicals (e.g. CF₃), one or more alkoxy (e.g.CH₃O) or one or more hydrocarbon-based radicals comprising one or moreketone units (e.g. CH₃CO—)

[0103] Examples of aryls that may be mentioned include phenyl, naphthyl,anthryl and phenanthryl radicals.

[0104] The term “arylalkyl” denotes an alkyl group as defined above,substituted with one or more aryl groups on its hydrocarbon-based chain,the aryl group being as defined above. Examples of these are benzyl andtriphenylmethyl.

[0105] The term “acyl” means a group R_(o)—CO— in which R^(o) representsalkyl as defined above; or a group Ar-CO— in which Ar represents an arylgroup as defined above, or alternatively an arylalkyl group in whicharyl and alkyl are as defined above and in which the aryl portion isoptionally substituted, e.g. with an alkyl.

[0106] The term “alkenyl” means a linear or branched, substituted orunsubstituted, unsaturated hydrocarbon-based chain containing at leastone olefinic double bond, and more preferably only one double bond. Thealkenyl group preferably contains from 2 to 8 and better still from 2 to6 carbon atoms. This hydrocarbon-based chain optionally comprises atleast one hetero atom such as O, N or S.

[0107] Preferred examples of alkenyl groups are allyl and homoallylgroups.

[0108] According to the invention, the term “alkynyl” means a linear orbranched, substituted or unsubstituted, unsaturated hydrocarbon-basedchain containing at least one acetylenic triple bond, and morepreferably only one triple bond. The alkynyl group preferably containsfrom 2 to 8 carbon atoms and better still from 2 to 6 carbon atoms.Examples that may be mentioned include the acetylenyl group and thepropargyl group. This hydrocarbon-based chain optionally comprises atleast one hetero atom such as O, N or S.

[0109] The expression “represents nothing” means that the substituents-T₃, or -T₄, respectively, are not present. Specifically, in formula(II), the nitrogen atom is trivalent, such that when A or B representsN, the nitrogen atom cannot contain an additional substituent.

[0110] Preferably, in the carbene ligands of formula (II):

[0111] T₃ and T₄ represent a hydrogen atom or together form a phenyl,

[0112] and/or T₁ and T₂, which may be identical or different-, represent(C₁-C₈)alkyl or (C₃-C₈)cycloalkyl-, preferably in the group of radicalscomprising: methyl, n-propyl, n-pentyl, neopentyl (—CH₂—C(CH₃)₃),cyclopentyl, cyclohexyl, adamantyl, allyl (—CH₂—CH═CH₂), methallyl(—CH₂—C(CH₃)═CH₂), propargyl, homopropargyl (—(CH₂)₂—C≡CH), or

[0113] or alternatively: —(CH₂)^(γ=1 to 4)-amine (for example N(CH₃)₂);or —(CH₂)_(γ=1 to 4)-alkoxy (for example O(CH₃)₂);

[0114] and/or A and B both represent a carbon atom.

[0115] According to one variant, the carbenes of formula (II)corresponding to the ligand L_(γ) in the catalyst -C- may contain atleast two fused nuclei, i.e. at least two substituents from T₁, T₂, T₃and T₄, located on two adjacent ring members, together form a saturatedor unsaturated hydrocarbon-based chain preferably containing from 3 to 6carbon atoms. The expression “saturated or unsaturated hydrocarbon-basedchain” means a linear or branched hydrocarbon-based chain possiblycontaining one or more unsaturations of olefinic double bond type or ofacetylenic triple bond type.

[0116] When the carbenes (II) contain fused nuclei, they thus correspondto one of the formulae below, in which (alk) represents a saturated orunsaturated hydrocarbon-based chain:

[0117] The ligands Lα and Lβ of the catalyst C of formula (I), belongingto the composition according to the invention, mayindependently-represent an alkynyl of formula (III.1) or an alkenyl offormula (III.2) substituted with radicals Z¹ to Z⁶ bearing at least oneelectron-withdrawing unit, which is active toward the π unsaturation ofLα and Lβ, to promote ligand binding with the metal M of the complex.

[0118] Advantageously, in formulae (III.1) and (III.2), theelectron-withdrawing residues are chosen from the group comprising:

[0119] in which:

[0120] R₁₇, R₁₈, R₁₉ and R₂₀ are a substituted or unsubstituted alkyl,alkenyl, alkynyl or trialkylsilyl, and n′ is between 1 and 50.

[0121] Examples of radicals Z¹ to Z⁶ that may be mentioned include:

[0122] those selected from the group comprising: —CN, —COOCH₃,—COOCH₂CH₃, —CONC₁₂H₂₅,

[0123] and, in the case where the substituents Z¹ and Z² form, in pairsand with the triple bond, in (III.1), a ring Cy1 and where Z³ to Z⁶ formin pairs, with or without the double bond, in (III.2), a ring Cy2, theserings Cy1 and Cy2 are independently and preferably chosen from the groupcomprising the following rings:

[0124] When Lα and Lβ together form a ligand Lδ of formula (IV), thisligand is preferably of the type in which Y₁ and Y₂ either bothrepresent CR_(a)R_(b) or both represent SiR_(c)R_(d), such-that saidcomplexes either have the formula (IV.1) or the formula (IV.2):

[0125] in which

[0126] the two R_(a), the two R_(b), the two R_(c) and the two R_(d) areidentical to each other, and R⁹═R¹²; R¹⁰═R¹⁴; and R¹¹═R¹³

[0127] According to one variant, the two R_(c) in (IV.2) together form:

[0128] (a) either a chain

[0129] in which n is an integer from 1 to 3; X is as defined above; andR and R′, which may be identical or different, take any of the meaningsgiven above for R_(d), it being understood that, when n is 2 or 3, onlyone silicon atom of said chain may be substituted with one or twoalkenyl or alkynyl groups; (b) or a saturated hydrocarbon-based chain,such that the two substituents R_(c), together with the two siliconatoms that bear them and X, form a 6- to 10-membered and preferably a 6-to 8-membered ring.

[0130] When the two R_(c) form the chain (a) in (IV.2), it is preferablefor n to be 1 or 2 (and better still n is 1) and for R═R_(d), the twogroups R_(d) borne by the two silicon atoms being identical. In thiscase, R_(d) preferably represents alkyl, for example methyl. Betterstill, in these compounds, R′ represents —CR₁₂═CR₁₃R₁₄; R₁₃═R₁₁;R₁₀═R₁₄; and R₁₂═R₉.

[0131] In this case, it is preferable for X to represent O in (IV.2).The ligand Lδ then has the formula:

[0132] Among these compounds, it is preferable for the two R_(d) to beidentical and advantageously to represent alkyl (for example methyl).

[0133] Preferably, n is 1 or 2 and R═R_(d), it being understood thatwhen n is 2, only one silicon atom of the chain O—(SiRR′—O)_(n)— may besubstituted with one or two alkenyl or alkynyl groups. Better still,R′=—CR₁₂═CR₁₃R₁₄ and R₁₃═R₁₁; R₁₀═R₁₄; and R₁₂═R₉.

[0134] When the two R_(c) form, together with the two silicon atoms andthe group X, the chain (b), it is preferable for the two groups R_(c) tobe an 8-membered ring. In this case, it is preferable for the two R_(d)to be identical. The ligand Lδ then has the formula:

[0135] in which T represents alkyl, i is an integer between 0 and 5, Tbeing located on one or more of the ring members 1, 2, 3, 4 and 5 of theabove formula.

[0136] Similarly, when Y₁ and Y₂ represent CR_(a)R_(b) in (IV.1), thetwo groups R_(a) linked to different carbon atoms can together form asaturated hydrocarbon-based chain (c), such that the two groups R_(a),together with the carbons that bear them and X, form a 6- to 10-memberedring. Preferably, the ring formed-is an 8-membered ring, in which casethe ligand Lδ then has the formula:

[0137] in which T represents alkyl; i is an integer between 0 and 5, Tbeing located on one or more of the ring members 1, 2, 3, 4 and 5 of theabove formula.

[0138] When R_(f) and/or R_(g) represents SiG₁G₂G₃, it is preferable forR_(f) and/or R_(g) to be trialkylsilyl, for example SiG₁G₂G₃ in whichG₁=G₂=G₃=alkyl.

[0139] Subgroups of the ligands Lδ of the metallic complexes (catalystC) that form part of the composition according to the invention consistof the complexes for which:

[0140] X═O; Y₁ and Y₂ independently represent SiR_(c)R_(d); or

[0141] X═NR_(e); Y₁ and Y₂ independently represent CR_(a)R_(b); or

[0142] X═NR_(e); Y₁ and Y₂ independently represent SiR_(c)R_(d); or

[0143] X═CR_(f)R_(g); Y₁ and Y₂ independently represent CR_(a)R_(b); or

[0144] X═CR_(f)R_(g); Y₁ and Y₂ independently represent SiR_(c)R_(d).

[0145] Among these ligands Lδ of formula (IV), the ones that arepreferred are those for which:

[0146] when X represents O, Y₁ and Y₂ independently representSiR_(c)R_(d); or

[0147] when X represents NR_(e), Y₁ and Y₂ independently representCR_(a)R_(b); or

[0148] when X represents CR_(f)R_(g), Y₁ and Y₂ independently representCR_(a)R_(b).

[0149] In practice, X represents O and Y₁ and Y₂ independently representSiR_(c)R_(d) in the ligand Lδ of formula (IV).

[0150] In the context of the invention, the expression “independentlyrepresent” means that the designated substituents are either identicalor different.

[0151] For example, R₁₀, R₁₁, R₁₃ and R₁₄ are hydrogen atoms in theligands Lδ of formula (IV).

[0152] Preferred meanings of R₉ and R₁₂ are especially a hydrogen atom;an alkyl group; an aryl group optionally substituted with alkyl; and acycloalkyl group optionally substituted with alkyl. Among thesepreferred meanings, it is particularly advantageous for R₉ and R₁₂ whichare identical, to represent a hydrogen atom; (C₃-C₈)cycloalkyl or(C₁-C₈)alkyl.

[0153] For example, the diolefinic ligand Lδ of formula (IV) issymmetrical, i.e. R₁₀═R₁₄; R₁₁═R₁₃; R₉═R₁₂ and the two groups Y₁ and Y₂are either strictly identical to each other, —or Y₁═CR_(a)R_(b) andY₂═CR_(a)R_(b) in which the two R_(a) together form a symmetrical chain,or alternatively Y₁=SiR_(c)R_(d) and Y₂=SiR_(c)R_(d) in which the twoR_(c) together form a symmetrical chain.

[0154] As regards the catalyst C of the composition according to theinvention, a first particularly preferred group of metallic complexes offormula (I.1) below should be mentioned:

[0155] in which:

[0156] T₁ and T₂ are identical and are as defined above;

[0157] T₃ and T₄ are as defined above;

[0158] R_(c) and R_(d) are as defined above.

[0159] A second particularly preferred group of catalysts -C- of thecomposition according to the invention comprises the metallic complexesof formula (I.2) below:

[0160] in which:

[0161] T₁ and T₂ are identical and are as defined above;

[0162] T₃ and T₄ are as defined above;

[0163] R_(c) and R_(d) are as defined above.

[0164] A third particularly preferred group of catalysts -C- of thecomposition according to the invention comprises the metallic complexesof formula (I.3) below:

[0165] in which:

[0166] T₁ and T₂ are identical and are as defined above;

[0167] T₃ and T₄ are as defined above;

[0168] R_(c) and R_(d) are as defined above.

[0169] Besides the catalyst C, the composition according to theinvention comprises the two polyaddition-reactive polyorganosiloxanespecies, namely the POS -A- and the POS -B-. These species are chosenfrom POSs consisting of siloxyl units of general formula:

(R²⁰)_(x)SiO_(4-x/2)  (I′)

[0170] and/or of siloxyl units of formula:

(R²¹)_(y)(R²²)_(z)SiO_(4-y-z/2)  (II′)

[0171] in which formulae the various symbols have the following meaning:

[0172] the symbols R²⁰ and R²², which may be identical or different,each represent a group of nonhydrolyzable hydrocarbon-based nature, thisradical possibly being:

[0173] an alkyl or haloalkyl radical containing from 1 to 5 carbon atomsand comprising from 1 to 6 chlorine and/or fluorine atoms,

[0174] cycloalkyl and halocycloalkyl radicals containing from 3 to 8carbon atoms and from 1 to 4 chlorine and/or fluorine atoms,

[0175] aryl, alkylaryl and haloaryl radicals containing from 6 to 8carbon atoms and from 1 to 4 chlorine and/or fluorine atoms,

[0176] cyanoalkyl radicals containing 3 or 4 carbon atoms;

[0177] the symbols R²¹, which may be identical or different, eachrepresent a hydrogen atom, a C₂-C₆ alkenyl group, a hydroxyl group, ahydrolyzable atom or a hydrolyzable group;

[0178] x=an integer equal to 0, 1, 2 or 3;

[0179] y=an integer equal to 0, 1, 2 or 3;

[0180] z=an integer equal to 0, 1 or 2;

[0181] the sum y+z is between 1 and 3;

[0182] with the condition that the POS -A- Si-alkenyl comprises at leastone unit R²¹=alkenyl per molecule and the POS -B- Si—H comprises atleast one unit R²¹=hydrogen per molecule;

[0183] preferably

[0184] R²⁰=methyl; ethyl; propyl; isopropyl; butyl; isobutyl; n-pentyl;t-butyl; chloromethyl; dichloromethyl; α-chloroethyl; α,⊕-dichloroethyl;fluoromethyl; difluoromethyl; α,β-difluoroethyl; 3,3,3-trifluoropropyl;trifluorocyclopropyl; 4,4,4-trifluorobutyl;3,3,4,4,5,5-hexafluoropentyl; β-cyanoethyl; γ-cyanopropyl; phenyl;p-chlorophenyl; m-chlorophenyl; 3,5-dichlorophenyl; trichlorophenyl;tetrachlorophenyl; o-, p- or m-tolyl; α,α,α-trifluorotolyl; xylyls suchas 2,3-dimethylphenyl, 3,4-dimethylphenyl and even more preferablymethyl or phenyl, these radicals possibly being optionally halogenatedor alternatively cyanoalkyl radicals;

[0185] R²¹=hydrogen or vinyl.

[0186] These POSs -A- and -B- are, for example, respectively, apolyorganovinylsiloxane and a polyorganohydrogenosiloxane. The variousorganic substituents of the vinyl reactive groups and of the hydrogenare, for example, methyls or cyclohexyls. The hydrogens and vinyls areborne by siloxyl units M=[R₃SiO—] and/or D=[—(R)₂SiO—] and/orT=[—(R)SiO—]. These hydrogenated or vinyl-containing units M and D eachcomprise one or more H or vinyl, preferably only one.

[0187] The number of SiH or SiVi units per molecule is greater than orequal to 1, preferably at least equal to 10 and better still between 10and 100.

[0188] This can represent from 0.01% to 10% (preferably 0.1% to 2%) ofvinyl by weight for the POS -A- and from 0.001% to 5% (preferably 0.05%to 2%) of hydrogen by weight for the POS -B-.

[0189] Polymers that are suitable are polymethylhydrogenosiloxanescontaining —Si(CH₃)₃ end groups and polydimethylsiloxanes containing —Si(CH₃)₂H end groups, methylhydrogenodimethylsiloxane copolymerscontaining —Si(CH₃)₂H end groups, methylhydrogenomethyloctylsiloxanecopolymers and methylhydrogenocyclosiloxane polymers.

[0190] In general, the POSs -A- and -B- that may be used in the reactionhave an average molecular mass of between 1×10² and 1×10⁶ (g/mol).

[0191] For the POS -A-, this especially encompasses, in terms of dynamicviscosity at 25° C., ranges:

[0192] of POSs that are polyaddition-vulcanizable at elevatedtemperature (EVC), with a viscosity at least equal to 1×10⁵ mPa.s,preferably between 1×10⁶ and 1×10⁷ mPa.s, and even better, for the

[0193] and POSs that are polyaddition-vulcanizable at elevatedtemperature of the liquid silicone elastomer (LSR) type, with aviscosity preferably of between 1×10⁵ and 5×10⁵ mPa.s.

[0194] According to one preferred mode of the invention, the siliconecompositions concerned are POSs that are polyaddition-vulcanizable atelevated temperature (EVC) in which the POSs -A- may in practice have aviscosity at 25° C. of, for example, 2×10⁶ mPa.s, and the POSs -B- from10 to 5000 mPa.s (for example 300 mPa.s).

[0195] In these examples, the viscosity is measured using a Brookfieldviscometer according to the indications of AFNOR standard NFT 76 106 ofMay 1982.

[0196] All the viscosities considered in the present descriptioncorrespond to a “Newtonian” dynamic viscosity magnitude at 25° C., i.e.the dynamic viscosity that is measured, in a manner that is known perse, at a shear rate gradient low enough for the measured viscosity to beindependent of the rate gradient.

[0197] The composition according to the invention may also contain acertain number of standard ingredients, besides the POSs -A- and -B- andthe catalyst C, including, especially, at least one crosslinkinginhibitor -B- capable of stopping the polyaddition reaction and ofallowing the conservation of the one-component composition ABCD, in anot fully crosslinked state.

[0198] Thus, the invention relates to silicone compositions comprisingat least one inhibitor -D- in which the catalyst -C- is chosen from themetal complexes

[0199] of formula (I.1) below:

[0200] of formula (I.2) below:

[0201] in which:

[0202] T₁ and T₂ are identical and are as defined above;

[0203] T₃ and T₄ are as defined above;

[0204] R_(c) and R_(d) are as defined above;

[0205] Z¹ to Z⁶ are free of electron-withdrawing radical(s);

[0206] and/or of formula (I.3) below:

[0207] in which:

[0208] T₁ and T₂ are identical and are as defined above;

[0209] T₃ and T₄ are as defined above;

[0210] R_(c) and R_(d) are as defined above;

[0211] Z¹ and Z² are free of electron-withdrawing residue(s).

[0212] These compositions have long pot lives.

[0213] It should be noted that, for certain catalysts C, especiallythose comprising a carbene (II) and at least one (and preferably two)ligands Lα and Lβ of formula (III.1) or (III.2), it is not necessary touse an inhibitor.

[0214] Thus, the invention is also directed toward silicone compositionsfree of inhibitor -D-, in which the catalyst -C- is chosen from themetallic complexes:

[0215] of formula (I.2) below:

[0216] in which:

[0217] T₁ and T₂ are identical and are as defined above;

[0218] T₃ and T₄ are as defined above;

[0219] R_(c) and R_(d) are as defined above;

[0220] at least one of the substituents Z¹ to Z⁶ (preferably eachsubstituent) comprises at least one electron-withdrawing residue;

[0221] and/or of formula (I.3) below:

[0222] in which:

[0223] T₁ and T₂ are identical and are as defined above;

[0224] T₃ and T₄ are as defined above;

[0225] R_(c) and R_(d) are as defined above;

[0226] Z¹ and Z² are free of electron-withdrawing residue(s).

[0227] These inhibitor-free compositions are endowed—entirelyadvantageously and-unexpectedly—with long pot lives in an ambientatmosphere. The crosslinking takes place only at elevated-temperature.This advantage is economically fundamental and fundamental in terms ofthe ease of use and of storage.

[0228] Advantageously, the inhibitors -D- (if used) are selected from:

[0229] polyorganosiloxanes, which are advantageously cyclic, substitutedwith at least one alkenyl, tetramethylvinyltetrasiloxane beingparticularly preferred,

[0230] unsaturated amides,

[0231] alkyl, alkenyl or alkynyl maleates, diallyl maleate beingparticularly preferred,

[0232] acetylenic alcohols,

[0233] alkyl, alkenyl or alkynyl acetylenedicarboxylates,

[0234] and combinations thereof.

[0235] As regards the acetylenic alcohols (cf. FR-B-1 528 464 and FR-A-2372 874), it may be mentioned that they form part of the preferredhydrosilylation-reaction thermal blockers, and they have the formula:

R^(x)—(R^(y))C(OH)—C≡CH

[0236] in which formula:

[0237] R^(x) is a linear or branched alkyl radical, or a phenyl radical;

[0238] R^(y) is H or a linear or branched alkyl radical, or a phenylradical;

[0239] the radicals R_(x), R^(y) and the carbon atom located a to thetriple bond possibly forming a ring;

[0240] the total number of carbon atoms contained in R^(x) and R_(y)being at least 5 and preferably from 9 to 20.

[0241] Said alcohols are preferably chosen from those with a boilingpoint of greater than 250° C. Examples that may be mentioned include:

[0242] 1-ethynyl-1-cyclohexanol;

[0243] 3-methyl-1-dodecyn-3-ol;

[0244] 3,7,11-trimethyl-1-dodecyn-3-ol;

[0245] 1,1-diphenyl-2-propyn-1-ol;

[0246] 3-ethyl-6-ethyl-1-nonyn-3-ol;

[0247] 3-methyl-1-pentadecyn-3-ol.

[0248] These α-acetylenic alcohols are commercial products.

[0249] Such a retardant (D) is present in a proportion of not more than3000 ppm and preferably in a proportion of from 100 to 2000 ppm relativeto the total weight of the organopolysiloxanes (A) and (B).

[0250] As common families of common functional additives that may beused in the silicone compositions according to the invention, mentionmay be made of:

[0251] fillers,

[0252] hydroxylated POS oils that are useful as compatibilizers,

[0253] adhesion promoters,

[0254] adhesion modulators,

[0255] pigments,

[0256] heat-resistant, oil-resistant or flame-resistant additives (forexample metal oxides),

[0257] etc.

[0258] The fillers that may be envisaged are preferably mineral. Theymay consist of products chosen from siliceous (or nonsiliceous)materials.

[0259] As regards the siliceous materials, they may act as reinforcingor semireinforcing filler.

[0260] The reinforcing siliceous fillers are chosen from colloidalsilicas, combustion silica powders and precipitation silica powders, ora mixture thereof.

[0261] These powders have a mean particle size generally of less than0.1 μm and a BET specific surface area of greater than 50 m²/g,preferably between 150 and 350 m²/g.

[0262] Semireinforcing siliceous fillers such as diatomaceous earths orground quartz may also be used.

[0263] As regards the nonsiliceous mineral materials, they may interveneas semireinforcing mineral filler or as packing mineral filler.

[0264] Examples of these nonsiliceous fillers that may be used, alone oras a mixture, include carbon black, titanium dioxide, aluminum oxide,hydrated alumina, expanded vermiculite, nonexpanded vermiculite, calciumcarbonate, zinc oxide, mica, talc, iron oxide, barium sulfate and slakedlime.

[0265] These fillers have a particle size generally of between 0.001 and300 μm and a BET surface area of less than 100 m²/g.

[0266] In practical but nonlimiting terms, the fillers used may be amixture of quartz and silica.

[0267] The fillers may be treated with any suitable product.

[0268] In terms of weight, it is preferred to use an amount of filler ofbetween 20% and 50% and preferably between 25% and 35% by weightrelative to the constituents of the composition as a whole.

[0269] More generally, in quantitative terms, the compositions accordingto the invention amount to proportions that are standard in thetechnical field under consideration, given that the intended applicationmust also be taken into account.

[0270] According to another of its aspects, the present inventionconcerns, as novel products, complexes of formula (I), which are usefulespecially as catalysts -C- and in which the carbene of formula (II) issuch that:

[0271] T₃ and T₄ can form, together with A and B when these eachrepresent a carbon atom, an aryl as defined above, preferably a phenyl;

[0272] and/or T₁ and T₂ independently represent a monovalent radical offormula (V) below:

-V₁-V₂  (V)

[0273] in which:

[0274] V₁ is a divalent-hydrocarbon-based radical, preferably anoptionally substituted linear or branched C₁-C₁₀ alkylene,

[0275] V₂ is a monovalent radical chosen from the following group ofsubstituents:

[0276] alkoxy, —OR^(v) with R^(v) corresponding to hydrogen, alkyl oraryl

[0277] amine, preferably N(R^(v))₂ with R^(v) corresponding to hydrogen,alkyl or aryl

[0278] or alternatively T₁ and T₂ independently represent a monovalentradical of formula (W) below:

-W₁-ω-W₂  (W)

[0279] in which:

[0280] W₁ is a divalent hydrocarbon-based radical, preferably anoptionally substituted linear or branched C₁-C₁₀ alkylene,

[0281] ω represents:

—R^(α)C═CR^(α)—

[0282] with R^(α corresponding to H or alkyl or)

—C≡C—

[0283] W₂ is a monovalent radical chosen from the following group ofsubstituents:

[0284] R^(β)=alkyl or H;

[0285] Si-alkyl, Si-alkenyl or Si-alkynyl, preferably —Si(alkyl)₃;

[0286] alcohol, preferably —C(R^(ε))₂OH with R^(ε)=H or alkyl;

[0287] ketone, preferably

[0288] with R_(δ)=alkyl; alkenyl, alkynyl;

[0289] carboxyl, preferably

[0290] with R_(δ)=alkyl; alkenyl, alkynyl;

[0291] amide, preferably

[0292] with R^(β)=H, alkyl; alkenyl, alkynyl;

[0293] acyl, preferably

[0294] with R^(δ)=alkyl; alkenyl, alkynyl;

[0295] T₁ and T₂ preferably independently corresponding to a radical Wof the type

[0296] or alternatively to one of the following units: methyl,isopropyl, tert-butyl, n-pentyl, neopentyl, cyclopentyl, cyclohexyl,adamantyl, allyl, methallyl, propargyl or homopropargyl,

[0297] or alternatively the substituents T₁, T₂, T₃ and T₄ can form inpairs, when they are located on two adjacent ring members in formula(II), a saturated or unsaturated hydrocarbon-based chain.

[0298] A subject of the invention is also other novel metallic complexesof formula (I) in which:

[0299] Lγ is as defined above,

[0300] Lα and Lβ correspond independently to the compounds of formula(II), (III.1) or (III.2) as defined above.

[0301] Examples of these novel catalysts that may be mentioned include:

[0302] those of formula (I.2) below:

[0303] in which:

[0304] T₁ and T₂ are identical and are as defined above;

[0305] T₃ and T₄ are as defined above;

[0306] R_(c) and R_(d) are as defined above;

[0307] or those of formula (I.3) below:

[0308] in which:

[0309] T₁ and T₂ are identical and are as defined above;

[0310] T₃ and T₄ are as defined above;

[0311] R_(c) and R_(d) are as defined above.

[0312] It should be noted that, in these formulae (I.1), (I.2) and also(I.3), the platinum may be replaced with any metal M as defined above.

[0313] The-invention also covers any-catalytic composition comprising,as active material, one or more metallic complexes (I) as defined aboveand comprising at least one ligand Lα or Lβ (better still two ligands)of formula (III.1) or (III.2).

[0314] Such catalysts (especially hydrosilylation catalysts) have theparticular feature of being able to be formed in situ, in siliconecompositions of the type according to the invention, provided that theycomprise ligands Lα and Lβ, of formula (III.1) or (III.2), for exampleas inhibitor -D-. This or these ligands Lα and Lβ, of formula (III.1) or(III.2) are capable of displacing the initial ligands Lδ of the catalystC. Such catalysts are latent catalysts. The present invention obviouslycovers this case.

[0315] Another subject of the invention consists of a process for thehydrosilylation of olefins or of acetylenic derivatives (for examplehydrosilylation of one or more POSs -A- using one or more POSs -B-),characterized in that it consists in using the silicone composition asdefined above and/or the catalytic composition also described above.

[0316] According to one advantageous variant in which at least onelatent catalyst as described above is used, use is made of a siliconecomposition according to the invention, as presented above andcomprising at least one inhibitor -D- allowing the in situ formation ofat least one metallic complex comprising at least one ligand Lα or Lβ,of formula (III.1) or (III.2).

[0317] Surprisingly, when the hydrosilylation is performed using ascatalysts the metallic complexes prepared by the process according tothe invention, formation of these side products is greatly limited. Moreparticularly, a strong reduction in the level of isomers formed, andalso a faint coloration, resulting from the decomposition of thecatalyst, are observed.

[0318] The hydrosilylation reaction may be performed in a solvent or inthe absence of solvent. As a variant, one of the reagents may act assolvent: for example, the compound containing an ethylenic double bondor containing an acetylenic triple bond.

[0319] Suitable solvents are solvents that are miscible with thecompound containing an Si—H unit.

[0320] Under the conditions of the hydrosilylation reaction, thecatalytic complex should be dissolved in the reaction medium.

[0321] Examples of solvents that may be used for the hydrosilylation areespecially aliphatic hydrocarbons (such as pentane, hexane, heptane,pentamethylheptane or petroleum distillation fractions); aromatichydrocarbons (such as benzene, toluene and xylenes: ortho-xylene,para-xylene and meta-xylene); halogenated aliphatic or aromatichydrocarbons (such as tetrachloroethylene); or ethers (such astetrahydrofuran or dioxane).

[0322] The hydrosilylation reaction may be performed at a temperature ofbetween 15° C. and 300° C., for example between 20 and 240° C., betterstill between 70 and 200° C., especially between 50 and 150° C. and verypreferably between 100 and 100° C.

[0323] The relative amount of unsaturated compound and of compoundcontaining an Si—H unit may be controlled so as to ensure reaction ofall the unsaturations with Si—H bonds.

[0324] Generally, the molar ratio of the unsaturations to the Si—H bondsranges between 1:100 and 10:1.

[0325] According to the invention, the hydrosilylation reaction isperformed in the presence of a catalytic amount of one or more complexesaccording to the invention. The term “catalytic amount” means less thanone molar equivalent of platinum relative to the amount of unsaturationspresent in the reaction medium.

[0326] In general, it suffices to introduce into the reaction mediumless than 1000 ppm, preferably less than 100 ppm and better still lessthan 50 ppm of platinum, calculated relative to the total mass of theunsaturated compound and of the compound containing Si—H units.

[0327] As regards the preparation of the composition according to theinvention, it is a matter of using and mixing together the compounds-A-, -B-, C, optionally -D- and one or more other conventionaladditives.

[0328] The mixing operations are entirely within the capability of theperson skilled in the art.

[0329] The POSs -A- and -B-, the inhibitors -D- and the other standardadditives, such as fillers, are commodities that are entirely availableor accessible to those skilled in the art.

[0330] As regards the metallic complexes (I) forming the catalysts C, ithas been seen above that the catalysts -C- comprising complexes:

[0331] with Lα and/or Lβ, of formula (III.1) or (III.2), may be obtainedfrom complexes (I) in which Lγ is of formula (II) and Lα and Lβ are offormula (IV), these ligands being displaced in situ with inhibitors -D-of formula (III.1) or (III.2).

[0332] These complexes (I) in which Lγ is of formula (II) and Lα and Lβare of formula (IV) are conventionally prepared, for example fromcomplexes known in the prior art by ligand exchange, i.e. by addition ofthe appropriate carbene of formula II to a metallic complex of the metalM, in solution, referred to as the precursor complex.

[0333] Examples of suitable precursor complexes include the Karstedtcomplex of formula:

Pt₂[ViMe₂Si—O—SiMe₂Vi]₃

[0334] in which Vi represents a vinyl radical.

[0335] The complexes of formula I are generally prepared from precursorcomplexes containing, as ligand, at least one diolefinic compound offormula (IV.P):

[0336] in which R₁, R₂, R₃, R₄, R₅, R₆, X, Y₁ and Y₂ are as definedabove for formula I.

[0337] These ligands are either commercially available or are easilyprepared by a person skilled in the art from commercial compounds.

[0338] When X represents NR_(e) and Y₁ and Y₂, independently of eachother, represent CR_(a)R_(b), the compounds of formula (IV.P) haveamines that are easily prepared by performing standard processes oforganic chemistry. Thus, when R_(a) is different than a hydrogen atom,these amines may be readily prepared from the corresponding primaryamine of formula R_(a)NH₂ via the action of suitable chlorides,preferably in the presence of an organic or mineral base.

[0339] When the diolefin (IV.P) is symmetrical (i.e. R₄═R₃; R₅═R₂;R₁═R₆; and Y₁═Y₂), R_(e)NH₂ is reacted with two equivalents of achloride of formula:

Cl—CR_(a)R_(b)—CR₃═CR₁R₂  (IV.P′)

[0340] in the presence of a base.

[0341] When the diolefin (IV.P) is dissymmetrical, it is preferable toprotect the amino group of R_(a)NH₂ with a suitable conventionalprotecting group P before reacting the resulting compound of formulaR_(e)NHP with a chloride of formula (IV.P″):

Cl—CR_(a)R_(b)—CR₃═CR₁R₂ (IV.P″)

[0342] in the presence of a suitable base.

[0343] Next, after deprotection, the resulting amine is reacted with achloride of formula (IV.P′″):

Cl—CR_(a)R_(b)—CR₄═CR₅R₆  (IV.P′″)

[0344] so as to obtain the expected amine.

[0345] In formulae IV.P′, IV.P″ and IV.P′″ above, the substituents R₁,R₂, R₃, R₄, R₅ and R₆ are as defined for formula I; R_(a) and R_(b) areas defined above.

[0346] The protecting groups P for the amine functions and thecorresponding deprotection methods are described in Protective Groups inOrganic Synthesis, Greene T. W. and Wuts P. G. M., published by JohnWiley & Sons, 1991, and in Protecting Groups, Kocienski P. J., 1994,Georg Thieme Verlag.

[0347] When R_(e) represents a hydrogen atom, it is desirable to select,as starting compound, the amine of formula IV.Q below, protectedbeforehand on the amino function with a protecting group P as definedabove:

NH₂—CR_(a) ²R_(b) ²—CR₃═CR₁R₂  (IV.Q).

[0348] The protected amine IV.Q is reacted with a chloride of formula VIas defined above, preferably in the presence of a base, and, afterdeprotection of the amino function, to give the expected compound offormula IV.P is isolated.

[0349] Examples of suitable bases include an organic base chosen fromtriethylamine, diisopropylamine, pyridine and N,N-dimethylaniline or amineral base such as NaOH, KOH, NaHCO₃, Na₂CO₃, KHCO₃ and K₂CO₃.

[0350] When X represents O and Y represents CR_(a)R_(b), the compoundsof formula (IV) are ethers. These ethers are commercially available orprepared in a manner that is known per se from commercially availablecompounds.

[0351] The compounds of formula IV in which X represents CR_(f)R_(g) andY represents CR_(a)R_(b) are diolefins that are readily available tothose skilled in the art by synthesis or are commercially available.

[0352] The compounds of formula IV in which X represents NR_(a) in whichR_(a) represents H or alkyl; R₁═R₆; R₂═R₅; R₃═R₄; andY₁═Y₂═SiR_(c)R_(d), may be prepared via the action of an amine R_(a)—NH₂with two equivalents of a silyl chloride of formula:

ClSiR_(c)R_(d)—CR₃═CR₁R₂

[0353] in which R_(c), R_(d), R₁, R₂ and R₃ are as defined above.

[0354] The compounds of formula IV in which X represents NR_(a), R_(a)being as defined above in formula I; Y₁=Y₂=SiR_(c)R_(d) in which R_(d)is as defined above in formula I; the two groups R_(c) together form thechain:

—NR_(a)—(SiR_(d)R_(c) ^(o)—NR_(a))_(n)—

[0355] in which R_(a) and R_(d) are as defined above; n represents aninteger from 1 to 3; R_(d) ^(o) represents —CR₃═CR₁R₂; R₁═R₆; R₂═R₅ andR₃═R₄, may be prepared by reacting the amine R_(a)—NH₂ with the silylchloride of formula:

Cl₂SiR_(d)—CR₃═CR₁R₂

[0356] in which R_(d), R₁, R₂ and R₃ are as defined above.

[0357] The compounds of formula IV in which X represents O and Y₁ and Y₂represent SiR_(c)R_(d) are linear, branched or cyclic siloxanes that arecommercially available or that may be prepared from commercialcompounds, by performing standard processes of the prior art. Examplesof preferred siloxanes of formula IV are ViMe₂SiOSiMe₂Vi and (MeViSiO)₃,the second formula representing a cyclosiloxane in which Vi representsvinyl.

[0358] In the case of the symmetrical compounds of formula IV, i.e.those in which R₁═R₆; R₂═R₅; R₃═R₄ and Y₁=Y₂, one of the followingsynthetic variants may be performed.

[0359] (Variant a): For the preparation of said symmetrical siloxanes offormula IV for which R₁, R₂, R₃, R_(c) and R_(d) are independentlychosen from alkyl, aryl, alkenyl and alkynyl, a silyl chloride offormula Cl₂SiR_(c)R_(d) may be reacted with an organometallic compoundof formula:

CR₁R₂═CR₃—Mg-Hal

[0360] in which R₁, R₂ and R₃ are as defined above and hal represents ahalogen atom, under the usual reaction conditions using magnesiumreagents.

[0361] (Variant b): For the preparation of said symmetrical siloxanes offormula IV for which R₁═R₂═R₃═H and R_(c) and R_(d) are chosen fromalkenyl, alkynyl, aryl and alkyl, a silyl chloride of formulaCl₂SiR_(c)—CH═CH₂ may be-reacted with an organometallic compound offormula:

R_(d)—Mg-hal

[0362] in which R_(d) is as defined above and hal represents halogen.

[0363] A person skilled in the art may refer to J. Gen. Chem., USSR,1977, 47, 1402-1406 to perform this variant.

[0364] (Variant c): For the preparation of said symmetrical siloxanes offormula IV in which R₁═R₃═H and R₂ represents alkyl, a siloxane offormula:

H—SiR_(c)R_(d)—O—SiR_(c)R_(d)H

[0365] may be reacted with two equivalents of an acetylenic hydrocarbonof formula H—C≡C—R₂ in which R₂ is as defined above.

[0366] Cyclic siloxanes of formula IV are described in U.S. Pat. No.4,593,084.

[0367] The compounds of formula IV in which X represents CR_(f)R_(g) andY₁ and Y₂ independently represent —SiR_(c)R_(d) may be prepared byperforming a process analogous to one of those described in:

[0368] J. of Organometallic Chemistry, 1996, Vol. 521, 99-107 (thisprocess being particularly suitable for preparing the symmetricalcompounds of formula IV in which Y₁=Y₂; R_(f)=R_(g)=H; R_(c) and R_(d)represent alkyl or aryl optionally substituted with alkyl; R₃ representsa hydrogen atom; alkyl; or optionally substituted aryl; and R₁ and R₂are chosen-from a hydrogen atom and alkyl);

[0369] J. of Organometallic Chemistry, 1997, Vol. 545-546, 185-189 (thisprocess being particularly suitable for preparing symmetrical compoundsof formula IV in which Y₁=Y₂; R_(f)=R_(g)=Cl or Br; R_(c) and R_(d)represent alkyl; R₁=R₂=R₃=a hydrogen atom);

[0370] J. Chem. Soc., Perkin Trans II, 1987, p. 381 (this process beingmore particularly suitable for preparing the symmetrical compounds offormula III in which Y₁=Y₂; R_(f)=R_(g)=SiG₁G₂G₃; R_(c) and R_(d)represent alkyl; R₁=R₂=R₃=a hydrogen atom).

[0371] The carbenes of formula II may be prepared by deprotonation ofimidazolium salts, tetrazolium salts, triazolium salts or pyrazoliumsalts, depending on the case, under the action of a base.

[0372] These reactions may be represented schematically as follows:

[0373] In these reaction schemes, T₁, T₂, T₃, T₄, A and B are as definedabove for formula I and X⁻ represents an anion.

[0374] The nature of the anion X⁻ is not critical according to theinvention. The anion X⁻ is the anion derived from a mineral or organicBrönsted acid (protic acid). Usually, the anion X⁻ is derived from anacid with a pKa of less than 6. Preferably, X⁻ is derived from an acidwith a pKa of less than 4 and better still less than 2. The pKa valuesthat are involved herein are the pKa values of the acids as measured inwater.

[0375] Examples of acids are the carboxylic acids of formula G_(o)—COOHin which G_(o) represents alkyl, for example (C₁-C₂₂)alkyl; or aryl, forexample (C₆-C₁₈)aryl optionally substituted with one or more alkyl,preferably one or more (C₁-C₆)alkyl; the sulfonic acids of formulaG_(o)SO₃H in which G_(o) is as defined above; and the phosphonic acidsof formula G_(o)PO₃H in which G_(o) is as defined above; other acids areHF, HCl, HBr, HI, H₂SO₄, H₃PO₄ and HClO₄.

[0376] Preferred examples-of carboxylic acids are acetic acid, benzoicacid and stearic acid. A preferred sulfonic acid that will be mentionedis benzenesulfonic acid, and a preferred phosphonic acid that will bementioned is phenylphosphonic acid.

[0377] According to the invention, the anions X⁻ derived from acids HF,HCl, HBr, HI, H₂SO₄, HBF₄ and H₃PO₄ are more particularly preferred.

[0378] Thus, anions X⁻ that are particularly preferred according to theinvention are halide, sulfate, hydrogen sulfate, phosphate, hydrogenphosphate and dihydrogen phosphate anions. Anions that may also bementioned include tetrafluoroborates and hexaphenylphosphate.

[0379] The bases that may be used for the deprotonation of the salts offormula VIII are strong bases chosen from alkali metal hydrides, alkalimetal hydroxides, alkali metal carboxylates, alkali metal alkoxides andalkali metal amides.

[0380] Examples of suitable bases are thus sodium hydride, sodiummethoxide, potassium tert-butoxide and lithium diisopropylamide, andmixtures thereof.

[0381] The deprotonation reaction is preferably performed in a solventcapable of at least partially dissolving the starting salt of formulaVIII and also the other reagents.

[0382] The nature of the solvent also depends on the strength of thebase. Specifically, in the case of a strong base and of particularlyreactive starting salts, it may be necessary to perform the process atlow temperature.

[0383] Generally, the reaction temperature is between 40 and −78° C.,preferably between 30 and −50° C. and better still between 25 and −40°C., for example between 20 and −30° C.

[0384] Solvents that may be used in the carbene preparation process arecyclic or noncyclic ethers, such as diethyl ether, diisopropyl ether,tetrahydrofuran, dioxane, dimethoxyethane or diethylene glycol dimethylether.

[0385] Other solvents that may be used are dimethyl sulfoxide,dimethylformamide, dimethylacetamide, hexamethylphosphorylamide:[(CH₃)₂N]₃PO and hexamethylphosphoramide [(CH₃)₂N]₃P.

[0386] The carbenes of formula II in which A and B both represent acarbon atom may also be prepared by reducing the corresponding thionesof formula IX:

[0387] This reaction was described by N. Kuhn in Synthesis, 1993, 561.Preferably, the reaction is performed in a solvent of the ether or amidetype, as defined above, at a temperature of between 50 and 150° C., inthe presence of potassium.

[0388] The starting salts of formula VIII may themselves be prepared byreacting the corresponding imidazoles, pyrazoles, triazoles andtetrazoles with a suitable acid.

[0389] The nature of the anion X⁻ in the salts of formula VIII dependson the acid Used in this step. The acids that may be used are, forexample, those listed above and from which X⁻ is derived.

[0390] Another method for synthesizing the salts of formula VIII inwhich A=B=-C- is described in U.S. Pat. No. 5,077,414.

[0391] This process comprises the reaction of an α-dicarbonyl compound Xof formula:

[0392] in which T₃ and T₄ are as defined above, with HCHO and two aminesof formulae. T₁—NH₂ and T₂—NH₂ in the presence of a suitable acid.

[0393] Other methods for preparing the salts of formula VIII areproposed in Chem. Eur. J. 1996, 2, n^(o) 12, pages 1627-1636 and Angew.Chem. Int. Ed. Engl. 1997, 36, 2162-2187.

[0394] The compounds of formula IX may be prepared by condensing asuitable thiourea of formula XI:

[0395] with an α-hydroxy ketone of formula XII:

[0396] in which T₁, T₂, T₃ and T₄ are as defined above. Suitableoperating conditions are described especially by N. Kuhn in Synthesis,1993, 561.

[0397] According to one particularly preferred embodiment of theinvention, the metallic complex of the invention has the formula:

[0398] in which Lγ is as defined above.

[0399] A simple method for preparing this complex consists in reactingthe carbene L with the Karstedt catalyst of average formulaPt₂[ViMe₂Si—O—SiMe₂Vi]₃ in which Vi represents a vinyl radical.

[0400] This reaction may be performed in bulk or in a solvent.

[0401] Examples of suitable solvents are cyclic or noncyclic ethers,such as diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane,dimethoxyethane or diethylene glycol dimethyl ether; amides such asdimethylformamide or dimethylacetamide; and aromatic hydrocarbons (suchas toluene or xylenes, but more particularly toluene).

[0402] Advantageously, the reaction is performed in an ether, andpreferably in tetrahydrofuran.

[0403] The reaction temperature usually ranges between 10 and 50° C.,preferably between 15 and 35° C. and very preferably between 20 and 25°C.

[0404] It is desirable to perform the process in the presence of aslight excess of carbene relative to the platinum. Thus, the molar ratioof the carbene L to platinum generally ranges between 1 and 1.3 andpreferably between 1 and 1.1.

[0405] A simple way of performing the process consists in pouring, at asuitable temperature, a solution of the carbene in a solvent into areactor containing a solution of the Karstedt catalyst in this samesolvent.

[0406] The molarity of the carbene solutions and of the catalystsolution is not critical according to the invention.

[0407] According to one variant, this process consists essentially inplacing the following in contact:

[0408] at least one salt of formula (VIII):

[0409] in which:

[0410] A, B, T₁, T₂, T₃ and T₄ are as defined above;

[0411] Z₇ independently represents an anion derived from a Brönsted acid(protic acid) preferably chosen from the group comprising:

[0412] carboxylic acids of formula Go-COOH in which Go represents analkyl and advantageously a C₁-C₂₂ alkyl; an aryl, advantageously aC₆-C₁₈ aryl optionally substituted with one or more C₁-C₆ alkyl;

[0413] sulfonic acids of formula Go-SO₃H in which Go is as definedabove;

[0414] phosphoric acids of formula Go-PO₃H in which Go is as definedabove;

[0415] the following-mineral acids: HF, HCl, HBr, HI, H₂SO₄, H₃PO₄,HclO₄ and HBF₄, taken alone or in combination;

[0416] and mixtures thereof;

[0417] at least one precursor complex of formula (IVp) selected from thegroup comprising suitable precursor complexes (IVp) are the Karstedtcomplexes of formula:

Pt₂[ViMe₂Si—O—SiMe₂Vi]₃

[0418] in which Vi represents a vinyl radical;

[0419] at least one solvent (V);

[0420] and at least one base (VI).

[0421] Advantageously, the solvent V is chosen such that the solubilityof the salt (VIII) and of the base (VI) in said solvent (V) is at least1% weight/weight at 25° C., respectively.

[0422] The solvent (V) is chosen-from polar aprotic solvents with aboiling point at 1 atm of less than 150° C., preferably 120° C.,preferentially from the group comprising:

[0423] cyclic or noncyclic ethers and in particular tetrahydrofuran(THF), diethyl ether, diisopropyl ether, dioxane, dimethoxyethane ordiethylene glycol dimethyl ether;

[0424] dimethylformamide, dimethylacetamide, —hexamethylphosphorylamide:[(CH₃)₂N]₃PO and hexamethylphosphoramide [(CH₃)₂N]₃P;

[0425] THF being particularly preferred.

[0426] The base(s) (VI) is (are) chosen from strong bases capable ofdeprotonating the salt (VIII), preferably from the group comprising:

[0427] alkali metal hydrides, alkali metal hydroxides,

[0428] alkali metal carboxylates, alkali metal alkoxides and alkalimetal amides,

[0429] and even more preferably from the group comprising:

[0430] sodium hydride, sodium methoxide, potassium tert-butoxide andlithium diisopropylamide, and mixtures thereof;

[0431] The concentration of the base (VI) in the reaction medium, in M/1of solvent (V), is preferably:

10⁻⁶ ≦VI≦1

and even more preferably 10⁻³ ≦VI≦10⁻¹.

[0432] The salt (VIII) and the base (VI) are used in amounts such thatthe ratio R_(VI/VIII) of normality VI/VIII is defined as follows:

R_(VI/VIII)≦1

preferably 1≦R_(VI/VIII)≦5

and even more preferably 1≦R_(VI/VIII)≦3.

[0433] In summary, this process consists essentially in:

[0434] a) dissolving the salt (VIII) and compound (IVp) in the solvent(V),

[0435] b) incorporating the base (VI) in several portions into thesolution of (VIII) and (IVp) in (V),

[0436] c) stirring the reaction medium thus formed, preferably in theabsence of light, until compound (I) has formed,

[0437] d) recovering the formed compound (I), preferably by evaporation,

[0438] e) optionally, purifying,

[0439] f) optionally, drying.

[0440] Preferably, at least one of the steps a), b) and c), andpreferentially all three of them, is (are) performed at a temperature ofbetween 5 and 50° C., and preferably at room temperature.

[0441] The following are preferably used:

[0442] at least one salt (VIII) of formula:

[0443] in which:

[0444] T₁ and T₂ are identical and represent (C₁-C₈)alkyl or (C₃-C₈)cycloalkyl;

[0445] T₃ and T₄ are identical and represent hydrogen or togetherrepresent a phenyl;

[0446] Z₁ is a halogen, preferably Cl or I, or BF₄;

[0447] at least one Karstedt complex as defined in patent U.S. Pat. No.3,775,452, preferably a compound of formula (IVp):

[0448] in which:

[0449] R_(d) and R_(e) are identical and represent CH₃;

[0450] a solvent (V) comprising THF;

[0451] and at least one base (VI) comprising potassium tert-butoxide(KOt-Bu).

[0452] The catalysts thus prepared may be used in hydrosilylationreactions. They allow homogeneous catalysis of the reaction.

[0453] They also give access to one-component silicone compositions,preferably of polyaddition EVC type, which have much longer pot livesthan those prepared with standard platinum-based catalysts, this beingachieved using little or no inhibitors -D-.

[0454] The invention is illustrated in the light of the examples thatfollow.

EXAMPLES Example 1

[0455] 1—Preparation of the Carbene of Formula:

[0456] (cf. Chem. Eur. J. 1996, 2, 1627).

[0457] For this reaction, all the glassware used is oven-dried at 150°C. overnight and then cooled under argon.

[0458] The THF is distilled over sodium/benzophenone just before use.

[0459] A 100 ml three-necked flask is charged with 2.70 g (10 mmol) of1,3-dicyclohexylimidazolinium chloride and then purged with a stream ofargon, followed by suspending in 20 ml of THF. About 50 ml of ammoniaare then condensed at −78° C. into the three-necked flask, resulting inthe partial dissolution of the salt. The acetone/cardice bath is removedand 270 mg of 95% NaH (10.7 mmol, 1.07 eq.) are added slowly using asolids-addition funnel. Each addition of NaH is followed by asubstantial evolution of gas (H₂) and the salt in suspension graduallydissolves. The reaction mixture is stirred for 1 hour 30 minutes at thereflux temperature of the solvent. The ammonia is then evaporated offand a pale yellow solution is obtained along with a solid in suspension(NaCl). This solution, the carbene concentration of which is 0.5 M inthe THF, is used immediately to prepare the complexes.

[0460] 2—Preparation of the Platinum Complex of Formula (Catalyst C1):

[0461] A Karstedt solution containing 10% by weight of platinum (i.e.1.52 mmol of platinum) is prepared in accordance with the proceduredescribed in U.S. Pat. No. 3,775,452.

[0462] 3.2 ml of a 0.5 M solution of the carbene of formula:

[0463] in tetrahydrofuran are added dropwise using a dropping funnel to3 g of this solution, kept stirring and diluted in 10 ml oftetrahydrofuran. The addition is complete after 10 minutes. The reactionmixture is then stirred for 50 minutes at room temperature. Whereappropriate, the light amount of insoluble material is filtered off andthe reaction mixture is concentrated under vacuum.

[0464] After concentration, a pale yellow viscous residue is obtained.Over several hours, an abundant white solid precipitates from theresidual divinyltetramethyldisiloxane. This solid is filtered off andwashed with a few milliliters of hexamethyldisiloxane and then withpentane. 570 mg (60% yield) of an analytically pure white powder arethus obtained.

[0465] A fraction of this powder is recrystallized from adichloromethane/absolute ethanol mixture. The resulting crystals areanalyzed by X-ray diffraction. The analysis confirms the structure ofthe complex obtained.

Example 2

[0466] 1—Preparation of the Carbene of Formula:

[0467] This carbene is prepared by performing the procedure illustratedin Example 1, paragraph 1, except that 2.7 g (10 mmol) of1,3-dicyclohexylimidazolinium chloride are replaced with 2.3 g (10 mmol)of 1,3-dimethylimidazolinium iodide.

[0468] 2—Preparation of the Platinum Complex of Formula C2:

[0469] This complex is prepared by performing the procedure of Example1, except that the carbene used as starting material has the formula:

[0470] After concentrating, a yellow paste is obtained. This paste isfiltered off and washed thoroughly with hot pentane. A whitish solid isisolated (35% yield), which is recrystallized from ethanol. Theresulting crystals are analyzed by X-ray diffraction. The analysisconfirms the structure of the complex obtained.

Example 3

[0471] Preparation of a Platinum Complex (III.2) of Formula (CatalystC3):

[0472] 500 mg (0.815 mmol) of the complex of Example 1 are placed in a50 ml one-necked round-bottomed flask equipped with a magnetic stirrer.The flask is purged with a stream of argon. The complex is thendissolved in 25 ml of anhydrous THF. 116 μl (135 mg; 0.94 mmol; 5 eq.)of dimethyl acetylenedicarboxylate are then injected. The reactionmixture is maintained at the reflux temperature of the solvent for twohours. After cooling to room temperature, the THF is evaporated offunder vacuum. The solid obtained is dissolved in the minimum amount ofdichloromethane. The crude product is chromatographed on a column ofsilica (eluent: 80/20 cyclohexane/ethyl acetate). After concentratingunder vacuum, the yellow flakes obtained are washed with 2-propanol andthen suction-filtered. 350 mg. (60% yield) of an analytically pureyellow powder are obtained.

Example 4

[0473] Preparation of one-component silicone compositions comprising thePOSs -A- and -B- and the catalysts —C1-, —C2- or —C3- of Examples 1, 2and 3, respectively.

[0474] In order to form a homogeneous phase with the silicone medium,the catalysts —C1-, —C2- and —C3- of Examples 1, 2 and 3 are introducedin solution in toluene. A base reaction system (M) is prepared by mixingtogether 100 grams of a polyorganovinylsiloxane containing 0.61% ofvinyl by weight and 27 grams of a polyorganohydrogenosiloxane containing0.17% by weight of hydrogen. For each example, the platinum is added tothe mixture (M) in a proportion of 80 ppm by weight. Depending on theexample, the nature of the catalyst and that of the inhibitor vary(tables 1 and 2 below). The Karstedt catalyst (platinum in oxidationstate zero dissolved in a vinylsilicone oil) is taken as the referencesystem.

[0475] The inhibitors used are the following:

[0476] Each system is evaluated by DSC and the gel time indicatedcorresponds to the time taken for the reaction mixture to set to asolid.

[0477] The results obtained are given in tables 1 and 2 below. TABLE 1Onset Exo- Tgel Test Catalyst Inhibitor [Inh]/[Pt] Temp. (° C.) therm (°C.) R.T. 60° C. 1 C2 / /  70  87 1 day (i) 2 C1 / /  75 111 1 day (ii) 3C2 I1 60 144 148 40 days 36 h 4 C2 I2 60 145 147 40 days 36 h 5 C1 I1 60137 149 40 days 36 h 6 C1 I2 60 141 149 40 days 36 h 7 C1 I3 60 142149 >40 days (ii) 8 C3 / / 115 130 >40 days (ii)

[0478] TABLE 2 Counter Onset Exo- Tgel Test Catalyst Inhibitor[Inh]/[Pt] (i) Temp. (° C.) therm (° C.) R.T. 60° C. 1′ Karstedt / /(ii) qq min. (iii) 2′ Karstedt I1 60 92   96  5 days 5 h 3′ Karstedt I260 99.5 103.5 5 days 5 h 4′ Karstedt I3 60 79   84  1 day (ii)

Example 5

[0479] One-component EVC silicone composition according to the invention(all the parts are given on a weight basis).

[0480] 5.1: Preparation

[0481] The following reagents are mixed together for two hours at roomtemperature (23° C.) in a Z-arm mixing blender:

[0482] 88 parts of a polyorganosiloxane, which is apoly(dimethyl)(methylvinyl)siloxane blocked at each of its two ends witha trimethylsiloxy unit, containing in the chain 720 ppm of Vi groups,with a viscosity of 5×10⁶ mPa.s at 25° C.,

[0483] 12 parts of a polyorganosiloxane, which is apoly(dimethyl)siloxane blocked at each of its two ends with adimethylvinylsiloxy unit, containing 120 ppm of Vi groups, with aviscosity of 2×10⁶ mPa.s at 25° C.,

[0484] 43 parts of treated combustion silica D₄ with a specific surfacearea of 60 m²/g,

[0485] 2 parts of a polydimethylsiloxane oil blocked at its ends withdimethylhydroxysiloxy units, with a viscosity of 50 mPa.s at 25° C.

[0486] The following are added to this preparation, on cylinder:

[0487] 2.82 parts of a poly(dimethyl)(methylhydro)siloxane oil blockedat each of its two ends with a dimethylhydrosiloxy unit, containing 45000 ppm of H groups, with a viscosity of 300 mPa.s at 25° C.,

[0488] 3.75 ppm of platinum metal supplied in the form of a platinum (0)complex,

[0489] 225 ppm of an inhibitor of the SiH/SiVi addition reaction, whichis diallyl maleate.

[0490] 5.2: Characterization of the Composition:

[0491] A fraction of the homogeneous mass obtained is used to measurethe mechanical properties of the silicone elastomer resulting from thehot vulcanization of the polyorganosiloxane composition. To do this, thefraction of the homogeneous mass retained for this purpose is thenvulcanized for 10 minutes at 170° C., working in a suitable moldallowing plaques 2 mm thick to be obtained. Plaques in nonannealed (NA)form are obtained. A fraction of the plaques then undergoes annealing(or aging) (A) for four hours at 200° C. Standardized samples are thentaken from these plaques as a whole and the following properties aremeasured:

[0492] Shore A hardness (SAH) according to standard DIN 53505

[0493] Breaking strength (BS) in MPa according to AFNOR standard NF T46002

[0494] Elongation at break (EB) in % according to the above standard

[0495] 100% modulus of elasticity (ME) in MPa according to the abovestandard.

[0496] Another fraction of the homogeneous mass obtained from theblender is used to measure the change in the Williams plasticity of thenonvulcanized silicone elastomer as a function of the storage time andof the temperature.

[0497] 5.3: Results

[0498] Mechanical Properties

[0499] The results are given in table 3 below: TABLE 3 AnnealedCharacteristics Nonannealed 4 h/200° C. Karstedt Pt SAH 46 56counterexample BS (MPa) 7.2 8.0 EB (%) 602 522 100% ME (MPa) 1.4 1.8Catalyst of SAH 47 58 example 1: Pt/cyclohexyl carbene BS (MPa) 7.9 8.7EB (%) 722 542 100% ME (MPa) 1.2 1.8

[0500] Comments:

[0501] The composition according to the invention gives an elastomerwhose mechanical properties are slightly higher than those obtained witha standard composition, without Pt catalyst/cyclohexyl carbene, but withKarstedt Pt.

[0502] Williams Plasticity

[0503] The results are given in table 4 below. TABLE 4 Characteristics25° C. 50° C. Karstedt Pt Time (days)  38  2 counterexample % increasein 100 100 consistency Catalyst of Time (days)  80  8 example 1: %increase in  66 100 Pt/cyclohexyl consistency carbene

[0504] Comments:

[0505] The pot life of the composition according to the invention ismarkedly longer than that obtained with a standard composition, withoutPt catalyst/cyclohexyl carbene, but with Karstedt Pt.

1. A hydrosilylation-crosslinkable silicone composition of at least onepolyorganosiloxane -A- (POS) bearing ethylenic and/or acetylenicunsaturation(s), using at least one polyorganohydrogenosiloxane -B-, inthe presence of a metallic catalyst -C- and optionally comprising atleast one inhibitor -D- of the hydrosilylation reaction; wherein thecatalyst -C- comprises at least one compound selected from the productsof formula (I):

in which M represents a metal chosen from the metals of group 8 of thePeriodic Table as published in the Handbook of Chemistry and Physics,65^(th) Edition, 1984-1985; L_(γ) represents a carbene of formula (II):

in which: A and B independently represent -C- or N, it being understoodthat when A represents N, then T₄ represents nothing, and when Brepresents N, then T₃ represents nothing; T₃ and T₄ independentlyrepresent a hydrogen atom; an alkyl group; a cycloalkyl group optionallysubstituted with alkyl or alkoxy; an aryl group optionally substitutedwith alkyl or alkoxy; an alkenyl group; an alkynyl group; or anarylalkyl group in which the aryl portion is optionally substituted withalkyl or alkoxy; or alternatively T₃ and T₄ may form, together with Aand B when these each represent a carbon atom, an aryl; T₁ and T₂independently represent an alkyl group; an alkyl group optionallysubstituted with alkyl; a perfluorinated alkyl group or an alkyl groupoptionally substituted with a perfluoroalkyl group; a cycloalkyl groupoptionally substituted with alkyl or alkoxy; an aryl group optionallysubstituted with alkyl or alkoxy; an alkenyl group; an alkynyl group; oran arylalkyl group in which the aryl portion is optionally substitutedwith alkyl or alkoxy; or alternatively T₁ and T₂ independently representa monovalent radical of formula (V) below: V₁-V₂  (V) in which: V₁ is adivalent hydrocarbon-based radical, V₂ is a monovalent radical selectedfrom the following group of substituents: alkoxy, —OR^(o) with R^(o)corresponding to hydrogen, alkyl or aryl amine, preferably N(R^(o))₂with R^(o) corresponding to hydrogen, alkyl or aryl T₁ and T₂independently represent a monovalent radical of formula (W) below:W₁-ω-W₂  (W) in which: W₁ is a divalent hydrocarbon-based radical,optionally substituted linear or branched C₁-C₁₀ alkylene, ω represents:—R¹C═CR¹—  with R¹ corresponding to H or alkyl or —C≡C—W₂ is amonovalent radical selected from the group of the following substituentsR²=alkyl, H; Si-alkyl or Si-alkoxy, preferably —Si(R³)₃ with R³=alkyl;alcohol, preferably —C(R⁴)₂OH with R⁴=H or alkyl; ketone, preferably:

 with R⁵=alkyl; carboxyl, preferably

 with R⁶=alkyl; amide, preferably

 with R⁷=H, alkyl; acyl, preferably

 with R⁸=alkyl; or alternatively the substituents T₁, T₂, T₃ and T₄ mayform in pairs, when they are located on two adjacent ring members informula (II), a saturated or unsaturated hydrocarbon-based chain; L_(α)and L_(β) 0 are ligands that may be identical or different, and eachrepresent:

 with, in these formulae (III.1) and (III.2): Z¹, Z², Z³, Z⁴, Z⁵, Z⁶each independently representing: a. hydrogen, b. a halogen, c. a cyano,d. a saturated or unsaturated electron-withdrawing hydrocarbon-basedgroup, optionally adjacent to the double or triple bond, e. two vicinalZ^(1 to 6) together optionally forming an electron-withdrawing ringadvantageously different than the carbene L_(γ) 0 of formula (II) andoptionally comprising hetero atoms; or the substituents Z¹ and Z²together form, in (III. 1), a monovalent alkenyl radical comprising atleast one electron-withdrawing residue optionally adjacent to the triplebond; or alternatively Z³ to Z⁶ form in pairs, in (III.2), a monovalentalkenyl radical comprising at least one electron-withdrawing residuepreferably adjacent to the double bond; or together form the ligand Lδof formula (IV):

in which: Y₁ and Y₂ represent, independently of each other, CR_(a)R_(b)or SiR_(c)R_(d); X represents O, NR_(e) or CR_(f)R_(g); R¹⁰, R¹¹, R¹³and R¹⁴, which may be identical or different, are selected from ahydrogen atom, an alkyl group and an aryl group optionally substitutedwith alkyl; R⁹, R¹², R_(a), R_(b), R_(c) and R_(d) are selectedindependently from a hydrogen atom; an alkyl group; an acyl group; anaryl group optionally substituted with alkyl; a cycloalkyl groupoptionally substituted with alkyl; and an arylalkyl group in which thearyl portion is optionally substituted with alkyl; R_(c) and R_(d) areindependently selected from alkyl; aryl optionally substituted withalkyl; cycloalkyl optionally substitued with alkyl; and arylalkyl inwhich the aryl portion is optionally substituted with alkyl; oralternatively when Y₁ and Y₂ independently represent SiR_(c)R_(d), twogroups R_(c) linked to two different silicon atoms together form a chainof formula:

in which n is an integer from 1 to 3; X is as defined above; R and R′,which may be identical or different, take any of the meanings givenabove for R_(e), it being understood that when n is 2 or 3, only onesilicon atom of said chain may be substituted with one or two alkenyl oralkynyl groups; or alternatively when Y₁ and Y₂ independently representSiR_(c)R_(d), two groups R_(c) linked to different silicon atomstogether form a saturated hydrocarbon-based chain, the two groups R_(c)together with said silicon atoms and X forming a 6- to 10-membered ring;or alternatively when Y₁ and Y₂ independently represent CR_(a)R_(b), twogroups R_(a) linked to different carbon atoms together form a saturatedhydrocarbon-based chain, the two groups R_(a) together with the carbonatoms that bear them and X form a 6- to 10-membered ring; and R_(f) andR_(g) represent, independently of each other, a hydrogen atom; an alkylgroup; an acyl group; an aryl group optionally substituted with alkyl; acycloalkyl group optionally substituted with alkyl; an arylalkyl groupin which the aryl portion is optionally substituted with alkyl; ahalogen atom; an alkenyl group; an alkynyl group; or a group SiG₁G₂G₃ inwhich G₁, G₂ and G₃ are, independently of each other, alkyl; alkoxy;aryl optionally substituted with alkyl or alkoxy; or arylalkyl in whichthe aryl portion is optionally substituted with alkyl or alkoxy.
 2. Thecomposition as claimed in claim 1, wherein M is a metal selected fromPt, Pd and Ni in oxidation state
 0. 3. The composition as claimed inclaim 1 wherein, in formula (II): T₃ and T₄ represent a hydrogen atom ortogether form a phenyl, and/or T₁ and T₂, which may be identical ordifferent, represent (C₁-C₈) alkyl or (C₃-C₈) cycloalkyl, wherein thegroup of radicals comprising: methyl, n-propyl, n-pentyl, neopentyl(—CH₂—C(CH₃)₃), cyclopentyl, cyclohexyl, adamantyl, allyl (—CH₂—CH═CH₂),methallyl (—CH₂—C(CH₃)═CH₂), propargyl, homopropargyl (—(CH₂)₂—C≡CH), or

or alternatively: —(CH₂)_(γ=1 to 4)-amine (for example N(CH₃)₂) or—(CH₂)_(γ=1 to 4)-alkoxy (for example O(CH₃)₂); and/or A and B bothrepresent a carbon atom.
 4. The composition as claimed in claim 1,wherein, in formulae (III.1) and (III.2), the electron-withdrawingresidues are selected from the group comprising:

in which: R₁₇, R₁₈, R₁₉ and R₂₀ are a substituted or unsubstitutedalkyl, alkenyl, alkynyl or trialkylsilyl, and n is between 1 and
 50. 5.The composition as claimed in claim 1, wherein: Z¹, Z², Z³, Z⁴, Z⁵ andZ⁶ are selected from the group comprising: —COOH₃, —COOCH₂CH₃,—CONC₁₂H₂₅, or and, in the case where the substituents Z¹ and Z² form,in pairs and with the triple bond, in (III.1), a ring Cy1 and where Z³to Z⁶ form in pairs, with or without the double bond, in (III.2), a ringCy2, these rings Cy1 and Cy2 are independently selected from the groupcomprising the following rings:


6. The composition as claimed in claim 1, wherein X represents O; Y₁ andY₂ independently represent SiR_(d)R_(e).
 7. The composition as claimedin claim 1, wherein R¹⁰, R¹¹, R¹³ and R¹⁴ are hydrogen atoms.
 8. Thecomposition as claimed in claim 1, wherein R⁹ and R₁₂ represent ahydrogen atom; an alkyl group; an aryl group optionally substituted withalkyl; or a cycloalkyl group optionally substituted with alkyl.
 9. Thecomposition as claimed in claim 1, wherein, in the ligands Lδ of formula(IV) of the catalyst C: when X represents O, Y₁ and Y₂ independentlyrepresent SiR_(c)R_(d); or when X represents NR_(e), Y₁ and Y₂independently represent CR_(a)R_(b); or when X represents CR_(f)R_(g),Y₁ and Y₂ independently represent CR_(a)R_(b), optionally, X representsO and Y₁ and Y₂ independently represent SiR_(c)R_(d)in the ligand Lδ offormula (IV).
 10. The composition as claimed in claim 1, wherein R⁹=R¹;R¹⁰=R¹³; R¹¹=R¹⁴ and either Y¹=Y, or Y¹=CR_(a)R_(b) and Y²=CR_(a)R_(b)in which the two R_(a) together form a symmetrical chain, oralternatively Y¹=SiR_(c)R_(d) in which the two R_(c) together form asymmetrical chain.
 11. The composition as claimed in claim 1, whereinthe catalyst -C- corresponds to formula (I.1) below:

in which: R⁹ and R¹² represent a hydrogen atom; a (C₁-C₈) alkyl group;or a (C₃-C₈) cycloalkyl group optionally substituted with (C₁-C₄) alkyl;T₁ and T₂ are identical and represent (C₁-C₈) alkyl or (C₃-C₈)cycloalkyl; R_(c) and R_(d) are as defined in claim
 1. 12. Thecomposition as claimed in claim 1, wherein the catalyst -C- is selectedfrom the metallic complexes of formula (I.2) below:

in which: T₁ and T₂ are identical and are as defined above; T₃ and T₄are as defined above; R_(c) and R_(d) are as defined above.
 13. Thecomposition as claimed in claim 1, wherein the catalyst -C- is selectedfrom the metallic complexes of formula (I.3) below:

in which: T₁ and T₂ are identical and are as defined above; are asdefined above; T₃ and T₄ are as defined above; R_(c) and R_(d) are asdefined above
 14. The composition as claimed in claim 1, wherein thePOSs -A- and -B- are selected from those consisting of siloxyl units ofgeneral formula: (R²⁰)_(x)SiO_(4-x/2)  (I′) and/or of siloxyl units offormula: (R²¹)_(y)R₂₂)_(z)SiO_(4-y-z/2)  (II′) in which formulae thevarious symbols have the following meaning: the symbols R²⁰ and R²²,which may be identical or different, each represent a group ofnonhydrolyzable hydrocarbon-based nature, this radical possibly being:an alkyl or haloalkyl radical comprising from 1 to 5 carbon atoms andcomprising from 1 to 6 chlorine and/or fluorine atoms, cycloalkyl andhalocycloalkyl radicals containing from 3 to 8 carbon atoms andcomprising from 1 to 4 chlorine and/or fluorine atoms, aryl, alkylaryland haloaryl radicals containing from 6 to 8 carbon atoms and comprisingfrom 1 to 4 chlorine and/or fluorine atoms, cyanoalkyl radicalscontaining 3 or 4 carbon atoms; the symbols R²¹, which may be identicalor different, each represent a hydrogen atom, a C₂-C₆ alkenyl group, ahydroxyl group, a hydrolyzable atom or a hydrolyzable group; x=aninteger-equal to 0, 1, 2 or 3; y=an integer equal to 0, 1, 2 or 3; z=aninteger equal to 0, 1 or 2; the sum y+z is between 1 and 3; with thecondition that the POS -A- Si-alkenyl comprises at least one unitR²¹=alkenyl per molecule and the POS -B- Si—H comprises at least oneunit R²¹=hydrogen per molecule; optionally R²⁰ methyl; ethyl; propyl;isopropyl; butyl; isobutyl; n-pentyl; t-butyl; chloromethyl;dichloromethyl; α-chloroethyl; α,β-dichloroethyl; fluoromethyl;difluoromethyl; α, β-difluoroethyl; 3,3,3-trifluoropropyl;trifluorocyclopropyl; 4,4,4-trifluorobutyl;3,3,4,4,5,5-hexafluoropentyl; β-cyanoethyl; γ-cyanopropyl; phenyl;p-chlorophenyl; m-chlorophenyl; 3,5-dichlorophenyl; trichlorophenyl;tetrachlorophenyl; o-, p- or m-tolyl; α,α,α-trifluorotolyl; xylylsoptionally 2,3-dimethylphenyl, 3,4-dimethylphenyl and methyl or phenyl,these radicals possibly being optionally halogenated or alternativelycyanoalkyl radicals; R²¹=hydrogen or vinyl.
 15. The composition asclaimed in claim 1, wherein the crosslinking inhibitors are selectedfrom: polyorganosiloxanes, which are optionally cyclic, substituted withat least one alkenyl, or tetramethylvinyltetrasiloxane, unsaturatedamides, alkyl, alkenyl or alkynyl maleates, or diallyl maleate,acetylenic alcohols, alkyl, alkenyl or alkynyl acetylenedicarboxylates,and combinations thereof.
 16. The composition as claimed in claim 1,which comprises at least one crosslinking inhibitor -D- and at least onecatalyst and in that at least one of the substituents Z₁ to Z₆ of this(or these) catalyst(s) -C- comprise(s) at least one electron-withdrawingresidue.
 17. The composition as claimed in claim 1, which is free ofcrosslinking inhibitor -D-, in that it comprises at least one catalystand in that this (or these) catalyst(s) -C- comprise(s) substituentS Z₁to Z₆ free of electron-withdrawing residues.
 18. A metallic complex offormula I as defined in claim 1, wherein: the carbene ligand L_(γ) offormula (II) is such that: T₃ and T₄ can form, together with A and Bwhen these each represent a carbon atom, an aryl as defined above,optionally a phenyl; and/or T₁ and T₂ independently represent amonovalent radical of formula (V) below: V₁-V₂  (V) in which: V₁ is adivalent hydrocarbon-based radical, V₂ is a monovalent radical selectedfrom the following group of substituents: alkoxy, —OR^(o) with R^(o)corresponding to hydrogen, alkyl or aryl amine, optionally N(R^(o))₂with R^(o) corresponding to hydrogen, alkyl or aryl, and/or T₁ and T₂independently represent a monovalent radical of formula (W) below:W₁-ω-W₂  (W) in which: W₁ is a divalent hydrocarbon-based radical,optionally substituted linear or branched C₁-C₁₀ alkylene, ω represents:—R¹C═CR¹—  with R₁ corresponding to H or alkyl or —C≡C— W₂ is amonovalent radical selected from the group of the following substituentsR²=alkyl, H; Si-alkyl or Si-alkoxy, preferably —Si(R³)₃− with R³=alkyl;alcohol, preferably —C(R⁴)₂OH with R⁴═ H or alkyl; ketone, preferably:

 with R⁵=alkyl; carboxyl, preferably

 with R⁶=alkyl; amide, preferably

 with R⁷=H, alkyl; acyl, preferably

 with R⁸=alkyl; T₁ and T₂ optionally independently corresponding to aradical W of the type

or alternatively to one of the following units: methyl, isopropyl,tert-butyl, n-pentyl, neopent.yl, cyclopentyl, cyclohexyl, adamantyl,allyl, methallyl, propargyl or homopropargyl, or alternatively thesubstituents T₁, T₂, T₃ and T₄ can form in pairs, when they are locatedon two adjacent ring members in formula (II), a saturated or aunsaturated hydrocarbon-based chain.
 19. The metallic complex of formula(I) as claimed in claim 18, having the following formula:

in which: R⁹ or R¹² represents a hydrogen atom; a (C₁-C₈) alkyl group;or a (C₃-C₈) cycloalkyl group optionally substituted with (C₁-C₄) alkyl;T₁ and T₂ are identical and represent (C₁-C₈) alkyl or (C₃-C₈)cycloalkyl; R_(c) and R_(d) are as defined in claim
 1. 20. A metalliccomplex of formula (I) in which: L_(γ) 0 is as defined in claim 1 Lα andLβ independently correspond to the compounds of formula (II), (III.1) or(III.2) as defined in claim
 1. 21. The metallic complex of formula (I)as claimed in claim 20, of formula (I) below:

in which: T₁ and T₂ are identical and are as defined above; T₃ and T₄are as defined above; R_(c) and R_(d) are as defined above.
 22. Themetallic complex of formula (I) as claimed in claim 20, of formula (I)below:

in which: T₁ and T₂ are identical and are as defined above; T₃ and T₄are as defined above; R_(c) and R_(d) are as defined above.
 23. Acatalytic composition comprising, as active material, one or moremetallic complexes as claimed in claim
 18. 24. A process for thehydrosilylation of olefins or acetylenic derivatives, comprising usingthe silicone composition as claimed in any one of claims 1 to 15 and/orthe catalytic composition as claimed in claim 23 claim
 1. 25. A processfor the hydrosilylation of olefins or acetylenic derivatives comprisingusing the composition as claimed in claim 1 comprising at least oneinhibitor -D- is used, allowing the in situ formation of at least onemetallic complex.